After a wellbore has been drilled, the wellbore typically is cased by inserting lengths of steel pipe (“casing sections”) connected end-to-end into the wellbore. Threaded exterior rings called couplings or collars are typically used to connect adjacent ends of the casing sections at casing joints. The result is a “casing string” including casing sections and connecting collars that extends from the surface to a bottom of the wellbore. The casing string is then cemented in place to complete the casing operation. After a wellbore is cased, the casing is often perforated to provide access to one or more desired formations, e.g., to enable fluid from the formation(s) to enter the wellbore.
Hydraulic fracturing is an operating technique where a fracturing fluid, typically water with selected additives, is pumped into a completed well under high pressure. The high pressure fracturing fluid causes fractures to form and propagate within the surrounding geological formation, making it easier for formation fluids to reach the wellbore. After the fracturing is complete, the pressure is reduced, allowing most of the fracturing fluid to flow back into the well. Some residual amount of the fracturing fluid may be expected to remain in the surrounding formation and perhaps flow back to the well over time as other fluids are produced from the formation. The volume and return rate of the fracturing fluid is indicative of the physical structure of the created fractures as well as the effective permeability for the newly-fractured completion zone.
During normal operations, the well produces a combination of fluids, typically including a desired hydrocarbon fluid (e.g., oil or gas) and water (i.e., “produced water”). The produced water can originate from multiple sources such as connate water from different formation layers, fracturing fluid, water injected from a remote well and/or steam injected from a remote well. These latter examples are typical of a steam or water flooding operation designed to force hydrocarbons to flow to the producing well.
In order to monitor and optimize hydraulic fracturing operations, and to better understand the relative permeabilities and physical structures of fractures resulting from hydraulic fracturing, it would be beneficial to determine the sources of water produced from each completion zone. For steam operations such as Steam-Assisted Gravity Drainage (SAGD) and water flooding operations, there is likewise a need to assess steam and water sweep areas. Despite these apparent benefits, there exists a need for improved systems or methods for such determinations.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereof do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.